The Curve is the affordable QWERTY model, and Tour is the higher-end QWERTY model for CDMA.

The higher-end Tour sports a better camera, as you noted, but also a much higher-resolution display, which is very noticeable when web browsing. You also get global roaming on the Tour, including global 3G.

Finally, the build quality is very different. I'm not saying the Curve is poorly built or won't last, but it feels plastic-y and cheap, whereas the Tour has a much higher-quality feel to it.